Electric-discharge apparatus.



.1 0 64 84 CROSS REFERENCE ExAr-mNER No. 882,218. PATENTED MAR. 17, 1908. P. H. THOMAS.

ELECTRIC DISCHARGE APPARATUS. nrmunmx rnmn FEB. a. 1903. i

WITNESSES: [NYE/(T08 tricity from conductors of dynamic electric- UNITED STATES PATENT OFFICE.

PERCY HITIIOMAS, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

ELECTRIC-DISCHARGE APPARATUS.

Application filed February 6. 1908. Serial No. 142,240. I 3

To all whom it may concern:

Be it known that I, PERCY H. Tnoms, a citizen of the United States, residing at Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Electric-Discharge Apparatus, of which the following is a specification. I

M invention relates to apparatus which is emp oyed for diverting static charges of elecity to ground without distur ing the normal 0 eration of such conductors and the ma 0 ery and apparatus connected thereto and to conducting bodies utilizable in such apparatus and elsewhere.

One object of my invention is to provide a simple and inexpensive device which shall be adapted to' relatively small, initial static discharges at comparatively low voltages and have also a sufiiciently low resistance to the passage of static electricity to discharge large quantities at high voltages freely and without dangerous rise of potential on the conductor of dynamic electricity and also without permitting the dynamo current to follow.

Another object of my invention is to provide a conducting body which comprises a large number of small conducting particles or elements so disposed as to provide separate paths for electric currents or discharges which are individually of high resistance.

It is to be understood that the terms static electricity and static charge, as here employed, are intended to embrace all charges of relatively high potential and small energy which are distinct from the energy that normally passes between the generator and the translating devices of. a system and which tend, by reason of their excessive and abrupt changes in potential to injure or destroy conductors or insulation.

Heretofore, in cases where the width of the spark-gap or the character of the materials between which it is formed has been relied upon both to permit of thestatic discharge and to prevent the passage of the dynamo current, difficulty has beenexperienced on account of the comparatively high electromotive force necessary to start the discharge, and where additional resistance has been included in series with the spark-gap and the latter has been so formed and proportioned as to enable the discharge to start at a rela- Specification of Letters Patent. Patented. March 17, 1908.

tivelylow electromotive 'force, a complete discharge of the line has been prevented or unduly impeded by reason of the large amount of. resistance included in series with the spark-gap or because of the form and disposition of such resistance.

I pro ose to overcome the above mentioned ifliculties by the means illustrated in the accom anying drawings, which will be now descri ed,

Figure 1 is a side elevation of one form of discharge device embodying my invention, the casing thereof being shoV/n in section. Fig. 2 is a viewsimilar to Fig. 1, but illus-'- tratinga modification. I

Referrin first to Fig. 1, the principal elements of t e device consist of two or more discharge plates 1 formed of a material or a composition of materials which has acomparatively high specific resistance. I have employed discharge plates formed of a mixture of graphite and fire clay with satisfactory resu ts, tion as an example, without intention 0 excluding other suitable materials and compositions of materials from the scope of my invention. The len h or width of these plates, or both, shou d be large as compared with their thickness and they may be used either with or without other plates 2 of good conducting material as terminals. Air gaps 3 may be provided between adjacent plates 1 or between said plates and the lates 2 or in both locations, as ma be foumFdesirable.

It is an essential c aracteristic of my invention that there shall be an opportunity for a large number of independent static discharges between the discharge plates and that each discharge ath shall have such resistance that the ynamo current cannot follow the static discharge. If this current cannot follow in any one of the various paths, it cannot follow at all, and on account of the numerous independent discharges, the resistance to the total discharge will be come paratively small.

In order to insure a large number of independentdischarges and a low resultant resistance, it is necessary to have the thick-' but I mention this com osi- I will occur if another dischar e passes in an- 60 lass or other suitable binder, the proporcurrent and other conditions of the circuit in discharge. An extreme example presenting conditions which my invention avoids would be the use of a long, high-resistance rod or cylinder. When a single discharge passes through the rod or cylinder, from end to end, the potential of the whole upper end is raised thereby, so that no considerable decrease in the 'total resistance to discharge other path parallel to the st. The material and thickness of the lates should be such that the resistance of t e path for each discharge may be sufficient to prevent the dynamo current from following.

The parts thus far described may be mounted in any suitable casing, that here shown being a two-part box or receptacle 4 of porcelain or other suitable insulating material rovided with binding posts 5;

In ig. 2, I have shown a single discharge plate 6 provided with backing terminal plates 7 of brass, or other suitable metal, to which the binding posts 8 are connected, the plates 6 and 7 being inclosed within a twopart casing or box 9 formed of porcelain or other suitable insulating material. In this form of my invention, the single discharge plate is ofgranular composition made up of a mixture of conducting and insulating particles so disposed that the equivalent of an external air gap is .obtained between the particles of conducting matter or over the surfaces of the non-conducting particles within the composition. The resistance of each of the several paths, through the material, results either from the high specific resistance or the small dimensions of the conducting particles or from both.

The ranular or comminuted conducting material may be any one of several varieties of carbon or other conducting material and the non-conducting material may be an incombustible cement or composition 0 cement and other non-conducting materials which will not become disintegrated in the use to which it is put and which will serve to maintain the conducting particles in their proper relative positions.

Discharge terminals having the structural and functional characteristics herein specified are not limited to specific conducting and non-conducting materials or to exact percentages of such materials or to any one specific method of manufacture, but, as an indication of What has been found satisfactory in practical operations, I may state that a suitable mixture may be composed of granular coke or carborundum, powdered s ar or other m a le non-con uc mg materia an water- 1ons of the ingredients of which the mixture is composed being subject to considerable variations in order to conform to the voltage,

connection with which the completed device is to be used. After the constituents have been thoroughly mixed, the mass may be compressed in suitable niold and then dried or baked, Since a hi Ti degree of heat is gfierall produced by 516 discharges to which the lilocks are subjected, it is desirable to employ conducting particles that do not readily disintegrate under such conditions, but the specific material, the size of the particles, the kind of insulating material and the specific binder may each or all depend upon any one or more of a variety of service conditions.

Since the essential feature of my invention is the provision of a very large number of discharge paths through any o all of which static discharges may take place and each of which is of such high resistance as will prevent the passage of dynamo current, the discharge block or plate may consist of a mass of high-resistance fibers and suitable insulating material in lieu of the high resistance 1granules and insulating material ab'ove specied. It is also conceivable that the desired mode of operation and result may be' attained by means of materials and compositions of materials which differ as to structure and arrangement from what I have specifically described and I desire and intend to in clude the same within the scope of my invention.

While the foregoing description relates mainly to apparatus employed for relieving electric circuits from static charges having such high potentials or such violent changes in potential as tend to destroy or seriously impair conductors and their insulation, it is not my intention to restrict the scope of my invention to such use.

It is conceivable that blocks or plates having the structural and electrical characteristics herein described may 'be advanta geously utilized in other relations and for other specific purposes, and I therefore desire and intend to include within the scope of my inventionall blocks or plates having the structural and electrical characteristics herein described, whatever may be the particular service' in which they are employed.

I claim as. my invention:

1. An electrical discharge device comprising a discharge plate having'large face area presented to the discharge as compared with its thickness and composed of intermingled particles of conducting material and nonconducting' material, the conducting articles being held in asubstantially invaria le relation but out of contact with each other.

2. An electrical discharge device comprising a discharge plate having large face area presented to the discharge as compared with its thickness and composed of particles of good conducting material and a mass of nonconducting binding material which holds the conducting particles in a substantially invariing a block or plate having comparatively vide discharge paths between them and havss2,21s a able relation but out of contact with each I oilzher and terminal plates for said discharge p ate.

3. An electrical discharge device comprising one or more plates of resistance material having great face area presented to the discharge as compared with its or their thickness and one or more air gaps, the specific resistance of the material of which the plate is composed being such that dynamo current cannot follow a static discharge at any point.

4. An electrical discharge device comprishigh resistance particles so disposed as to proing a large ace area presented to the discharge as compared with its thickness.

5. In an electrical discharge device, a plate or block composed of a mixture of conducting and non-conducting particles of such dimensions and so disposed that each conducting particle has a comparatively high resistance and discharges may take place between said particles, and having a large face area presented to the discharge as compared with its thickness.

In testimony whereof, I have hereunto subscribed my name this 31st day of January 1903.

PERCY H.'THOMAS. Witnesses WM. H. GAPEL, GEORGE H. STOCKBRIDGE. 

